Cat poo parasite could help fight cancer

Chris Page

A parasite found in cat poo could be the next weapon in fighting ovarian cancer tumours, a new study has found.

Toxoplasma gondii is found in cat poo and contaminated meat and an estimated third of Britons will be infected by toxoplasmosis at some point in their life, but most people won't notice it.

It is only a risk to the unborn children of pregnant women and those with a weakened immune system.

Now US scientists have found the specific proteins secreted by the parasite that cause the immune system in mice to attack established ovarian tumours.

The process works by exploiting the parasite's need not to kill off its host while ensuring its own survival.

One promising strategy in the fight against cancer is to use the body's own immune system to remove tumour cells.

But due to a phenomenon called immune tolerance, the immune system has a difficult time identifying which cells to attack.

In the new study by Geisel School of Medicine at Dartmouth in Hanover, New Hampshire, scientists built upon previous discoveries that a safe, non-reproducing vaccine strain of T. gondii could cure mice of several types of solid tumours.

It also Identified which parasite proteins and which immunological pathways are required to break immune tolerance.

Scientists then systematically deleted genes for secreted effector proteins, molecules that the parasite injects into a host cell to modulate the immune system during infection, and injected the altered parasites into mice with aggressive ovarian cancer.

Their results demonstrate that the specific proteins that T. gondii secretes before and after host cell invasion, respectively, control the development of an effective host antitumour response, and increase the survival of mice with ovarian tumours.

Using infectious infectious organisms to break tumour immune tolerance is a novel idea and may be key for treating cancer in the future.

Scientists are also exploring the bacterium Listeria monocytogenes to break the immune tolerance of pancreatic tumours

Professor of Microbiology and Immunology Dr David Bzik said: "Our results demonstrate that specialised effector proteins secreted by T. gondii both before and after host cell invasion trigger and coordinately control the development of a potent antitumour response.

by these T. gondii secreted effector proteins can reveal fundamental mechanisms controlling immunity to infection and can also identify relevant mammalian cell mechanisms as new targets for devising more effective therapies against highly aggressive solid tumours."